CLS (in)stability at speed

[yarand]

My 2007 CLS 500 (388bhp 5.5l) feels unstable at motorway speeds - it feels unsettled as though it is rocking from side to side. This situation applies even with the active suspension set at the ("hardest") setting II.
I mentioned this to my local Mercedes dealer when the car was in for a service, and they road tested the car on a motorway. They too noted the feeling. They then road tested another CLS and noted the same feeling and concluded that everything must be okay! I spoke to Mercedes UK customer services, who reported back that there is nothing to be done, because it is (obviously) typical with the model!
I exploded at this point - this is a car that, even with the UK speed limiter, is advertised as capable of 155mph! I for one would feel totally uncomfortable to drive the car at anything like those speeds (speed limits permitting) when the car feels so unstable.
Does anybody else have similar concerns with their CLS?

 

[BlackC55]

How is the tyre wear? Is the steering wheel straight? Has a wheel alignment been done?

 

[yarand]

How is the tyre wear? Is the steering wheel straight? Has a wheel alignment been done?

The car has 4 new Michelin SP2 tyres, and the tracking and alignment were recently checked. The issue feels more to do with the suspension as the car simply does not feel "stuck" to the road.

 

[wemorgan]

Could the issue be aerodynamic?
Are you missing an under-tray?
Though I'd be surprised if this was noticeable at 70mph

edit: I might also question MB ability to measure the geometry correctly. The dealers get pretty rough reports on this forum.

 

[lynall]

My car is rock steady at any speed even on the limiter, wifes car is the opposite we had a 4 wheel aligment done by elite tyres and it was better but now doesnt seem glued and also needs constant correction to keep a straight line.

I would recomend you contact wheels in motion who did my car excellent results and that was approx 8mths ago and its still fine at any speed.
Not cheap £150 iirc but was worth every penny.



Lynall

 

[saorbust]

That's weird - assuming no high cross wind.

I have exactly the same model as you and it's steady as a rock.

Try another dealer, and write to the UK MD. Totally unacceptable.

 

[davidbilyk]

Could be a suspension ecu fault I suppose, certainly doesn't sound a nice issue! Have you considered getting a diagnostic check?

 

[saorbust]

Hmm good point. They have Airmatic - might be something to do with that - sensor failure ? I had a bad vibration but that was easily solved - dealer had fitted new tyres, but hadn't balanced the wheels. Addition of weights by local tyre place, £10 later, sorted in 20 minutes.

 

[Brian WH]

That's weird - assuming no high cross wind.

I have exactly the same model as you and it's steady as a rock.

Try another dealer, and write to the UK MD. Totally unacceptable.

I agree, mine is ROCK Steady at any speed.

 

[Mactech]

One of the great attributes of the large Mercedes cars is their ability to cruise, ocean liner like, at high speed without being deflected by wind, speed or road surface. I have driven a number of CLS cars and none have shown anything like the instability you describe.
It is possibly a fault with the Airmatic, but much more likely a geometry or tyre issue.
The car is still in warranty, ensure that it is put right!

 

[grober]

I reckon its a fault [ software related maybe?] with the air suspension [ADS II???] -possibly not adjusting the ride height/damping at increased speed ?? e.g.

 

[Adam230K]

Is it doing mini nose dives in any direction? or is it general side-to-side wandering?

 

[evdok]

I had similar years ago on a E30 BMW 325i, turned out to be the tyres, man from pirelli met me at the tyre place with 4 new tyres, sorted that!

 

[Rory]

My 2007 CLS 500 (388bhp 5.5l) feels unstable at motorway speeds - it feels unsettled as though it is rocking from side to side.

....

Does anybody else have similar concerns with their CLS?

Completely different model - I have C270CDI Avantgarde Estate (on standard 16" wheels and suspension - and at 70ish mine has always been just as you describe. Dealer has looked at the car a couple of times and says it's fine. I find it irritating on long journeys.

I wonder if the cars are set up for high speed stability and are not in their ideal "zone" at 70? I needed to drive at high speed a while a ago and the car felt more stable than at 70, which is really just bumbling along.

I also had occasion to drive the M6 Toll road in streaming wet weather with significant surface water. I was doing 70ish (fast for the conditions) and the car felt imperious. My thought was perhaps the surface water somehow loaded everything up in the same way as high speed would do.

 

[hygt2]

I would probably bet on defective tyres. Have you had them inspected? Are the pressure correct?

 

[Brian WH]

Completely different model - I have C270CDI Avantgarde Estate (on standard 16" wheels and suspension - and at 70ish mine has always been just as you describe. Dealer has looked at the car a couple of times and says it's fine. I find it irritating on long journeys.

Irritating is not the word, UNACCEPTABLE would be my word for it.

It needs fixing NOW.

 

[whitenemesis]

Completely different model - I have C270CDI Avantgarde Estate (on standard 16" wheels and suspension - and at 70ish mine has always been just as you describe. Dealer has looked at the car a couple of times and says it's fine. I find it irritating on long journeys.

I wonder if the cars are set up for high speed stability and are not in their ideal "zone" at 70? I needed to drive at high speed a while a ago and the car felt more stable than at 70, which is really just bumbling along.

I also had occasion to drive the M6 Toll road in streaming wet weather with significant surface water. I was doing 70ish (fast for the conditions) and the car felt imperious. My thought was perhaps the surface water somehow loaded everything up in the same way as high speed would do.

Similar model to Rory but the Sport with bigger wheels, lower, firmer suspension. Mine can feel a little 'nervous' at speeds below approx 70mph. It is always very planted in corners and under braking but straight ahead has that 'twitchy' feel. Once above 70 - 80 it gets progressively more fluid and feels enormously competent. Even at much higher speeds it never gives me concern.

What you describe most certainly is not characteristic of any MB model all of which are designed for prolonged high speed cruising.

It's still under warranty get back to the dealer and insist it is corrected!

 

[DSLiverpool]

Before anyone gets overly anti MB the OP has put none spec tyres on the car and from my limited experience of driving a CLS55 for 2 years, occasional drive of a CLS320 and CLS350CGi the diesel car had pirellis and was horrible, the other two (mine especially) has MO Contis.

I would first put it on star and if NFF change the tyres to the ones MB designed the car to use

 

[timskemp]

I've driven the CLS at speed, it's as rock steady as the E it's based on. Sounds like a fault to me. As others have said, they are rock solid at 40, 70, 110, 140, 155. I find cars feel comfortable at certain speeds, for the Volvo that was about 105, for the Merc it's about 130. 70 is an easy lope along.

By the way my E has had goodyear, dunlop and nexen on it and none of those have caused issue. It now has aftermarket wheels and different nexen tyres, which I'll report on later...

I'd be looking at a steering or suspension fault - mine had a faulty power steering pump which was causing very variable assistance making it feel very unstable at speed.

 

[geoffd]

wandering cls

I'd agree with DSLiverpool - tyre choice can make hugh handling differences. I recently had a very similar problem with my SLK. Originally it had Dunlop SP Sport 2020 tyres, which are no longer available in my size. My local fitter suggested SP Sport 01s as replacements - result unbelievable wandering. I've now replaced with SP Sport 2000s and am back to the normal rock steady handling.

I believe my problem was because the SP Sport 01s are assymetric - could it be that the Michelins causing this issue are too ?

Geoff